As frustration sets in...

[poppa]

Not having alot of luck here. Cad/Zinc plating and I can't get a good finish. Doing some older car parts. Not a metallist (assuming it's mostly steel),not a mathematician (square inches),not an electrician(amps,volts,what's),so may have bitten off more than I can chew. Have the older cad/zinc kit,25 amp rectifier,fish tank heater.
1) How big of an area can I plate with this??
2) When I plated a brake booster (after blasting) I pulled it out and it seemed to have a milky/chauky substance that dried and streaked almost right away.
3)Zinc on a couple pieces looked ok when first removed but dulled awhile later
4) Figured out the 'don't remove from yellow chromate and nonchalantely take in the house to rinse(gets darker quick).Can I reblast this and do over?
5) Is there a "Plating for dummies" book available(it would fit right in with all my other dummie books).Parts were rinsed right away(may have been tap water though).
Any help would be appreciated.I am think of ordering new crystals and something for agitation.What's best for cleaning parts after blasting?Much more later(don't want to scare you off right away...after all ,this is only my first post!).Did you catch the 'what's' partSee the # 1 , I'm as cherry as I'll ever be.

[seanc]

You'll have to give us more specific data for some issues, but:

Have the older cad/zinc kit,25 amp rectifier,fish tank heater.
1) How big of an area can I plate with this??

Part size will depend on:

1. Rectifier: 25 amps will plate 250-300+ sq-inches (using old formula zinc)
2. Anode: anode size >= part size
3. Tank & electrolyte: well, it's gotta be big enough for the parts to fit comfortably & fully submerged

2) When I plated a brake booster (after blasting) I pulled it out and it seemed to have a milky/chauky substance that dried and streaked almost right away.

See #1. How big is the booster? How big are your anodes relative to booster? How many amps was it plated at?

3)Zinc on a couple pieces looked ok when first removed but dulled awhile later

Unless protected, raw zinc will corrode producing a dull white layer ("white rust"). It's relatively soft and will rub off fairly easily. Is this what you're seeing?

Zinc needs to be protected against "white rust". If you're not chromating, soak it in WD-40, or apply some sort of wax/other top coat.

4) Figured out the 'don't remove from yellow chromate and nonchalantely take in the house to rinse(gets darker quick). Can I reblast this and do over?

Possibly. If it's only the chromate you're not satisfied with, that might work. Otherwise, acid strip the zinc plate entirely, and do it all again. I've given up try to "fix" mistakes, found it far easier & better to re-do from the start.

What's best for cleaning parts after blasting?

It's best to thoroughly clean parts BEFORE blasting. Only raw metal & it's corrosion products should ever get into a blast cabinet.

Others may have different opinions, but this works great for me:

1. Clean, degrease, de-crud, strip paint, etc. Not one speck of contamination left anywhere.
2. If heavily rusted, soak in acid pickle (10-20% muriatic) to dissolve the heavy stuff. Rinse & dry.
3. Media blast. Go immediately from blasting to plating. Don't let the parts sit exposed for any more time than necessary to make the transition.
4. Rinse in running water
5. Dip in acid pickle (5-10% muriatic acid) for a few seconds (10-20 sec.) to activate the metal
6. Rinse again
7. plate

Sean

[poppa]

The booster will fit in the bottom of a 3.5 gal pail with .5 to .75 inches of clearance. I used two 4x8 anodes doing one side at a time.
Do I rub off the white rust dry?
Right now I can't go from blasting to plating.Blast at work , plate at home.
Will the acid solution you mentioned be correct to strip the zinc and chromate finish?
I think my prep work needs some work.Seems like I always have to run my solution through coffee filters.I will get some new crystals and have been thinking of a new container also.

Thanks for taking the time to reply.....

P.S.Glanced at your link,will read when time permits.

[seanc]

The booster will fit in the bottom of a 3.5 gal pail with .5 to .75 inches of clearance.

Well, I don't know how big a 3.5 gal pail is, so still can't visualize what you have going. There is no substitute for a good estimate of the booster surface area.

How much distance is there between anodes & booster? You certainly want a lot more than .5-.75" separation between them.

With 36" of anode, I'm getting the feeling though, that your booster is bigger than your anodes, which will give uneven and/or poor plating.

Do I rub off the white rust dry?

Rubbing it off is not a cure, it's just a means of identifying IF it's white rust that you're seeing.

The proper thing to do is PREVENT it from white rusting in the first place, by chromate, WD-40, wax, paint, etc.

Right now I can't go from blasting to plating.Blast at work , plate at home.

In that case, depending on how much time elapses in-between:

• a few hours - pickle the parts in mild muriatic acid right before plating. This will remove any minute surface rust that has developed.
• overnight - hit the fresh blasted parts w/WD-40 to prevent rusting. Degrease then acid pickle right before plating.

Will the acid solution you mentioned be correct to strip the zinc and chromate finish?

Yes. The stronger the solution, the faster it will strip. 15-20% is more than enough to strip parts w/in 5-15 minutes (just depends on how thick the plate is). When the parts stop fizzing, the zinc is gone.

Seems like I always have to run my solution through coffee filters.

Why? The electrolyte will get cloudy w/sediments, but still plates good. Filtering does remove the brightener (if you use it).

Sean

[poppa]

Thanks for your help. I will try this again when I get my new crystals. I'm sure I will have more questions then.....